©1997 by Eric Mazur Published by Pearson Prentice Hall Upper Saddle River, NJ ISBN No portion of the file may be distributed, transmitted in any form, or included in other documents without express written permission from the publisher.

Gravitation

Which of the following depends on the inertial mass of an object (as opposed to its gravitational mass)? 1. the time the object takes to fall from a certain height 2. the weight of the object on a bathroom-type spring scale 3. the acceleration given to the object by a compressed spring 4. the weight of the object on an ordinary balance

Two satellites A and B of the same mass are going around Earth in concentric orbits. The distance of satellite B from Earth’s center is twice that of satellite A. What is the ratio of the centripetal force acting on B to that acting on A ? 1. 1/8 2. 1/4 3. 1/2 4. √1⁄2 5. 1

Two satellites A and B of the same mass are going around Earth in concentric orbits. The distance of satellite B from Earth’s center is twice that of satellite A. What is the ratio of the tangential speed of B to that of A ? 1. 1⁄2 2. √1⁄ √2 5. 2

Suppose Earth had no atmosphere and a ball were fired from the top of Mt. Everest in a direction tangent to the ground. If the initial speed were high enough to cause the ball to travel in a circular trajectory around Earth, the ball’s acceleration would 1. be much less than g (because the ball doesn’t fall to the ground). 2. be approximately g. 3. depend on the ball’s speed.

A rock, initially at rest with respect to Earth and located an infinite distance away is released and accelerates toward Earth. An observation tower is built 3 Earth-radii high to observe the rock as it plummets to Earth. Neglecting friction, the rock’s speed when it hits the ground is 1. twice 2. three times 3. four times 4. six times 5. eight times 6. nine times 7. sixteen times its speed at the top of the tower.

The Moon does not fall to Earth because 1. It is in Earth’s gravitational field. 2. The net force on it is zero. 3. It is beyond the main pull of Earth’s gravity. 4. It is being pulled by the Sun and planets as well as by Earth. 5. all of the above 6. none of the above

A pendulum bob is suspended from a long pole somewhere on the northern hemisphere. When the pendulum is at rest, the combined action of gravitation and Earth’s rotation makes the bob 1. point straight down toward the center of Earth. 2. deviate toward the east. 3. deviate toward the west. 4. deviate toward the north. 5. deviate toward the south. 6. none of the above